Loss Tangent Measurements Research Articles

Determination of Complex Permittivity of Fly Ash for Potential Electronic Applications

Disposal of fly ash obtained from thermal power plants is a major environmental concern. Fly ash contains large proportions of silica and ferrites. Investigation of its prospects as an electronic material provides scope for enhanced fly ash utilization. This involves measurement of relative permittivity and loss tangent. Experiments are carried out at X band frequencies in TE10 mode using standard klystron waveguide setup. Shorted Waveguide Method is used to determine the complex permittivity. The complex transcendental equation obtained is solved using Genetic Algorithm. Experimental results are compared with theoretical estimates based on Landau Lifshitz Looyenga (LLL) equation.

Phase pure synthesis of BiFeO 3 nanopowders using diverse precursor via co-precipitation method

Amorphous powder of BiFeO 3 (BFO) was synthesized at low-temperature (80 °C) by co-precipitation method. Optimal synthesis conditions for phase pure BFO were obtained. Powders were calcined in the temperature range from 400 to 600 °C for 1 h. Iso-statically pressed powder was sintered at 500 °C for 2 h. Differential scanning calorimetric thermo-gram guided for phase transition, crystallization and melting temperatures. X-ray diffraction confirmed the amorphous nature of as synthesized powder and phase formation of calcined powders. Calcination at temperature ≥400 °C resulted in nano crystalline powders with perovskite structure. Average crystallite size increased with the increase in calcination temperature. Scanning electron microscopic studies revealed dense granular microstructure of the sintered samples. The sintered samples exhibited high dc resistivity at room temperature which decreased with the increase in temperature. Dielectric constant, dielectric loss tangent and ac conductivity measurements were carried out in the frequency range (10 Hz to 2 MHz). The samples responded weak electric and magnetic polarization at room temperature with unsaturated and hysteresis free loops, respectively.

Structural, Dielectric, and Magnetic Characterization of Nanocrystalline Ni–Co Ferrites

Spinel ferrites containing Nickel and Cobalt of composition with nominal formula Ni(1−x)Co(x)Fe2O4 (x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5) prepared by the coprecipitation method are reported. The single phase spinel formation of ferrites was confirmed by X-ray diffraction techniques. The lattice constants (ath) were calculated based on the ionic radii of the constituents. The calculated lattice constants are smaller than the measured, because for calculations ideal ionic radii are used. The particle size calculated from the Scherrer formula varied within 15 to 33 nm. The dielectric constant and dielectric loss tangent measurement were carried out at room temperature as a function of frequency from 100 Hz to 3 MHz. Both the dielectric constant and dielectric loss tangent increased with increase in cobalt concentration. Ferrimagnetic transition temperature as a function of Co concentration was measured with the low field ac susceptibility apparatus. The ferrimagnetic transition (Tc) was observed in the temperature range 573 to 720 K. The Tc decreased with the addition of Co concentration. The effect of Co concentration on the magnetic properties was investigated using a vibrating sample magnetometer (VSM). It was found that both magnetic saturation (Ms) and coercivity (Hc) increase with Co concentration.

Dielectric modeling of multiphase composites

In this paper effective medium theory based on Clausius–Mossoti relation was used to predict dielectric properties of multiphase composite system. The composite consisted of E-glass fibers (plain weave S-glass, J.B. Martin) embedded in bisphenol A diglycidylether epoxy matrix (D.E.R. 324, D.O.W. chemicals) with hollow ceramic spherical inclusions (SF 14, P.Q. Corp.) at different volume fractions. In many engineering applications, materials with designed dielectric properties are often sought. An important question in engineering design of a composite material is how the overall properties of the composite depend on those of the individual constituents. Mixing the epoxy resin with hollow ceramic inclusions can effectively reduce dielectric constant of the resin, which is often desirable, rendering composites as good candidates for many applications, especially in telecommunications. Compensation for degradation of mechanical properties of matrix (due to inclusion insertion) is obtained by embedding fibers into the mixture. Measurements of dielectric constant and loss tangent for this multiphase composite system were conducted in the region between 0.1 and 100 kHz range using DEA 290 (T.A. Instruments) dielectric analyzer and experimental results are presented. Good correlation between analytical model and experimental results was observed throughout all frequency range of investigation.

Dielectric loss and magnetic behavior of combustion synthesized ferrite-ferroelectric composites

Spinel-type nickel cadmium ferrite and perovskite-type barium strontium titanate ferroelectric and their composites have been grown by combustion route. The variation of loss tangent with frequency in the range 100 Hz to 1 MHz was studied. The ac conductivity was derived from dielectric constant (e′) and loss tangent (tanδ) measurements. The nature of conduction is discussed on the basis of small polaron hopping model. The dependence of saturation magnetization (Ms) and remanent magnetization (Mr) of the composites is also reported.

Superposition of Inductive and Capacitive Coupling in Superconducting LC Resonators

We present an experimental investigation of lumped-element superconducting LC resonators designed to provide different types of coupling to a transmission line. We have designed four resonator geometries including dipole and quadrupole configured inductors connected in parallel with low loss SiNx dielectric parallel-plate capacitors. The design of the resonator allows a small change in the symmetry of the inductor or grounding of the capacitor to allow LC resonators with: 1) inductive coupling, 2) capacitive coupling, 3) both types of coupling, or 4) greatly reduced coupling. We measured all four designs at a temperature of 30mK at different values of power. We compare the extracted data from the four resonator types and find that both capacitive and inductive coupling can be included and that when left off, only a minor change in the circuit design is necessary. We also find a variation in the measured loss tangent of less than a few percent, which is a test of the systematic precision of the measurement technique.

Multifrequency Measurements of Dielectric Properties Using a Transmission-Type Overmoded Cylindrical Cavity

Characterization of complex permittivity has been performed using TM0mn modes in an overmoded cylindrical cavity. The Rayleigh-Ritz technique is employed to find a rigorous relationship between the relative permittivity, resonant frequency, and the dimensions of the resonant structure. A functional relationship between the structure's S -parameters and the system's unloaded Q factor is established. Complex permittivities of several materials, including polytetrafluoroethylene, high-density polyethylene, cross-linked polyethylene, and sodium naphthalene treated PTFE, are measured at room temperature. Their accuracy is assessed by comparing the results with those obtained from other well-known techniques. An error analysis is also presented to estimate the errors incurred due to the uncertainties in cavity dimensions, resonant frequency, scattering parameters, and the conductivity of the coating layer. In this measurement, an accuracy of better than ±0.5% is attained in measurement of the relative permittivity, while the uncertainty in the measured loss tangent is within a range of ±6%. For properly chosen sample dimensions, this presented method is examined to be very useful for measurement of the complex permittivity over the widely used microwave frequency range, such as the L-, S-, C-, and X-bands.

English

The effect of aging on Sr 2+ modified Lead Zirconate Titanate (PSZT) ceramics have been studied. Aging was assessed by the measurement of dielectric constant and dielectric loss tangent as a function of time and temperature. Dielectric constant and dielectric loss tangent measured at different temperature range. Absolute rate of aging and relative rate of aging was determined. The PSZT ceramic showed sharp dielectric peak at temperature 300 o C. The result showed that with increased temperature both the dielectric constant and rate of aging increased. Defence Science Journal, 2010, 60(6), pp.683-686 , DOI:http://dx.doi.org/10.14429/dsj.60.55

Effect of Ce and La substitution on dielectric properties of bismuth titanate ceramics

Effect of Ce and La substitution on the microstructure and dielectric properties of bismuth titanate (BT) ceramics was investigated. Bismuth titanate ceramics (Bi 4− x A x Ti 3O 12) (A = Ce or La; x = 0, 0.5, 1) were processed by sintering of pressed pellets, prepared from nanopowder synthesized by the modified sol–gel method. Pure and La modified bismuth titanate ceramics have single Bi 4Ti 3O 12 phase of Aurivillius type, whereas a small amount of Bi 2Ti 2O 7 pyrochlore phase appears in Ce modified bismuth titanate ceramics. In the same time addition of La and Ce improved sinterability of BT ceramics. The results of the measurement of dielectric constant and loss tangent at different frequencies (100 Hz–1 MHz) as a function of temperature reveal that Ce modified ceramics has a diffuse phase transition. Temperature T m , corresponding to the maximum value of the dielectric constant, is shifted to higher temperature and the maximum value of the dielectric constant is decreased with increasing frequency, which indicate that relaxor behavior is caused by Ce substitution.

Influence of copper substitution on magnetic and electrical properties of MgCuZn ferrite prepared by microwave sintering method

Polycrystalline MgCuZn ferrites with chemical formula Mg 0.50-xCu xZn 0.50Fe 2O 4 ( x = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25 and 0.30) were prepared by microwave sintering method. These powders were calcined, compacted and sintered at 950 °C for 30 min. Structural, microstructural and elemental analyses were carried out using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectrometry (EDS), respectively. The lattice parameter is found to increase with increasing copper content. A remarkable densification is observed with the addition of Cu ions in the ferrites. The sintered ferrite was characterized for initial permeability, dielectric constant and dielectric loss tangent and ac conductivity measurements. The temperature variation of the initial permeability of these samples was carried out from 30 °C to 200 °C. The dielectric constant, dielectric loss tangent and ac conductivity have been measured in the frequency range of 100 Hz to 1 MHz. Initial permeability and dielectric constant were found to increase and dielectric loss decreased with Cu substitution for Mg, up to x = 0.20. The ferrite powder prepared is suitable for the application in multilayer chip inductor due to its low-temperature sinterability, good magnetic properties and low loss at high frequency.

Laboratory measurement of dielectric constant and loss tangent of Indian rock samples

The data on dielectric properties of Indian rock samples are very sparsely reported in the literature. Keeping this in view, we have carried out laboratory measurements of the dielectric constant and loss tangents of some samples of sandstone, quartzite, limestone, marble, dolerite and basalt. LCR bridge and Q-meter have been employed for measurements in the frequency range 10 - 10' Hz. The results have been presented in the form of variation of these parameters with frequency which show characteristic features. Observations on the effect of moisture content of these samples on the dielectric properties have also been reported. Further, correlation of petrographic studies of rock samples with measured variations of dielectric properties has been attempted.

Anisotropy of dielectric losses in Al2O3 and SiO2 single crystals

The procedure and results of measurements of the dielectric loss tangent using the dielectric resonator technique on azimuthal modes of the HE (quasi-E) and EH (quasi-H) types are considered. The measurements were performed for uniaxial anisotropic single crystals of Al2O3 (at a frequency of 11 GHz) and SiO2 (at 39 GHz) in a temperature range of 80–373 K and for an isotropic single crystal of Y3Al5O2 (YAG) at room temperature in a frequency range of 9–15 GHz. The proposed method revealed the anisotropy of dielectric losses in Al2O3 and SiO2 single crystals in the temperature range studied. According to this, losses along the optical axis of these crystals are lower than in the transverse plane. In the YAG crystal, the Q values for modes of the two types with the same frequency are close, which corresponds to isotropic losses. The dielectric losses in YAG increase in proportion to the frequency.

Condition Assessment of Power Transformers Using Loss Tangent Measurements

Mineral oil, cellulose paper and pressboard are the main insulation materials in a power Transformer. During service, increase of moisture, as the by -products ageing and increases the risk of insulation failure. This paper presents the possibility to use loss tangent (or power factor) and capacitance (tanδ and C) measurements as an estimate of the 'wetness' of aged transformer insulation. Firstly, oil, paper and pressboard samples were aged under laboratory conditions and their tan S and dielectric constant (er) values were measured. Applying the tanδ and er obtained onto a transformer insulation model, the tanδ and C of transformer were calculated and the effects of insulation geometry, moisture content (MC) of pressboard, oil conductivity (σ oil) and insulation temperature under test were established. It was found that tanδ and C values of a transformer strongly dep ended on its insulation geometry and the temperature. If the temperature is fixed, the change of tanδ value of a transformer can be a direct measure of moisture in pressboard for 'wet' and 'extremely wet' conditions. For a 'dry ' transformer, the σoil oil value is needed as an additional known parameter in order to estimate accurately the moisture in pressboard.

Elastic properties of epoxy system coatings on aluminum substrate

In the present work elastic properties of the epoxy system coatings deposited on aluminum-based alloy substrate were investigated using internal friction methods i.e. i) vibrating reed technique (frequency about 100 Hz) and ii) torsion pendulum (1 Hz). The apparent Young's modulus γ 2 E ( γ — adhesion coefficient, E — Young's modulus of the coating) was determined for different state of substrate surface and curing temperatures. It was shown that γ 2 E correlates linearly with the bond shear strength obtained from tensile tests by applying Instron machine (destructive method). Moreover, the dependence γ 2 E versus curing temperature shows a maximum at 350 K. Isothermal measurements of mechanical loss tangent Q − 1 ( t) versus curing time show that the curing reaction of the epoxy material is observed as an asymmetric peak whose position shifts towards shorter times with increasing curing temperatures. Activation energy of the curing process determined from this shift is found to be E a = (51 ± 3) kJ/mol.

Parasitic Effect of the (Ba,Sr)TiO3 Thin Film for Tunable Microwave Device Application

The (Ba 0.6 ,Sr 0.4 )TiO 3 (BST) thin films were deposited on the Pt bottom electrode (Pt/Ti/SiO 2 /Si) by radio frequency magnetron sputter. After that, a 100 nm-thick Pt thin film was deposited by electron beam evaporator as the top electrode to form metal/insulator/metal (MIM) structure. The capacitance-voltage characteristics were recorded to study the voltage-controlled capacitance. The frequency dispersion was found in the measurements of capacitance and loss tangent. The reason should be the parasitic effect of series resistance and parasitic inductance. The simulations of the four-element modified model were performed to evaluate the influences of the measurement frequency and parasitic resistance on the electrical measurement. The simulation results indicate that the capacitance and loss tangent increase with increasing the measurement frequency. The tunability slightly increases with increasing measurement frequency while the figure of merit seriously degrades with increasing measurement frequency and series resistance. The correct electrical properties of the tunable microwave device should be measured at low frequency (< 100 kHz) or extracted with the four-element modified model.

Tape Casting and Dielectric Properties of Zn2Te3O8‐Based Ceramics with an Ultra‐Low Sintering Temperature

The suitability of dielectric ceramics made of zinc tellurate (Zn2Te3O8) and titanium dioxide (TiO2) with an ultra‐low sintering temperature (650°C) for tape casting and thus for the multimodule technique with Al electrodes was investigated. The properties of the tape before and after sintering as well as the amount of organic additives for the casting process and a thermal analysis of the tape up to 1000°C are reported. In addition, electrodes on a multilayer module made on stacked tapes were prepared using Al paste and postfiring, followed by relative permittivity and loss tangent measurements to verify the electrical performance of the whole structure. The dielectric properties of the stacked module without any electrodes were also measured. The results show that the composition is well suited for the tape process but extra care should be taken especially with the proper sintering temperature for optimized electrical performance.

Anomalously high capacitance of β-rhombohedral boron induced by structural defects

Capacitance and dielectric loss tangent measurements have been carried out for β-rhombohedral boron within the frequency range 102 – 104 Hz and temperature interval 77 – 373 K. Different specimens were studied: high-purity macrocrystals, vapor-liquid-grown faceted crystals, zone-melted single crystals, and crucible-melted polycrystals. Within the whole ranges of measurements, the capacitance of all samples was 10–60 times larger than their geometric capacitance. Temperature dependences of the capacitance reveal two-level step-like behavior. Location of levels is independent from the applied electric field frequency, but at higher frequencies, the capacitance steps shift to lower temperatures. For all frequencies, an abrupt rise in capacitance takes place at one and same temperature ∼ 290 K. At low temperature, dielectric losses are negligible, but they increase towards the room temperature. At ∼ 290 K (i.e., simultaneously with the abrupt rise in capacitance) their value abruptly falls down. Dielectric properties of β-rhombohedral boron are discussed on the basis of generalized barrier model of the heterogeneous semiconductor within its three-layer version. Planar defects like twins and stacking faults characteristic for real crystals are assumed to produce local elastic stresses sufficient for the local lowering in conductivity due to the piezoresistive effect. Consequently, layers adjacent to the planar defects should represent low-conducting inclusions in the relatively high-conducting matrix. In addition, the lesser-conducting barrier layers should appear at their boundaries. Effect at ∼ 290 K seems to be related with a symmetry-restoring phase transition driven by the occupation patterns of certain atomic sites in β-rhombohedral crystalline boron lattice.

Split-Post and Split-Cylinder Resonator Techniques: A Comparison of Complex Permittivity Measurement of Dielectric Substrates

We provide an overview of two nondestructive techniques, the split-post and split-cylinder resonator, which are under consideration as standard test methods for measuring the relative permittivity and loss tangent of bare low-temperature cofired ceramic (LTCC) substrates over the frequency range of 1–30 GHz. The capabilities and limitations of the split-post and split-cylinder resonator are outlined, and the level of agreement between the two techniques is examined through comparison of the relative permittivity and loss tangent measurements of a fused silica and an LTCC substrate.

Co-sintering of barium strontium titanate (BST) thick films inside a LTCC substrate with pressure-assisted sintering

Screen-printed ferroelectric BST thick films were co-fired inside a LTCC substrate by employing pressure-assisted sintering (PAS). Sintering pressure and time were varied and their effect on the microstructure and dielectric properties of the film was studied. Sintering conditions for the fabrication of buried BST thick films were experimentally defined and parallel plate capacitors were successfully fabricated inside a LTCC substrate. The relative permittivity ( ɛ r) of the films at 10 kHz varied from 188 to 220 depending on the sintering conditions, and the maximum tunability of the films was 44% (5.7 V/μm). The measured loss tangent (tan δ) at zero bias was 0.005.

Dielectric investigations and ac conductivity of polyvinyl alcohol films doped with europium and terbium chloride

Differential scanning calorimetry (DSC) was used to identify the phase transitions of polyvinyl alcohol (PVA) doped with europium chloride (EuCl 3) and terbium chloride (TbCl 3). The dielectric constant and the loss tangent behavior of the investigated samples were studied as a function of temperature in the frequency range 1–100 kHz. The detailed analysis of the results showed that dielectric dispersion consists of both dipolar and interfacial polarization. The temperature coefficient of permittivity (TCP) and the electrical dipole moment ( μ) were calculated. Also, the activation energy for the glass relaxation process from the dielectric loss tangent measurements was calculated. Measurements of the ac conductivity as a function of frequency at different temperatures indicated that the correlated barrier hopping (CBH) model is the most suitable mechanism for the ac conduction behavior. The ac parameters, such as hopping distance ( R, R min), polaron binding energy ( U M) and Coulombic barrier height ( U h) were calculated.